Problem: If $a + b + c = 9$ and $x + y + z = -4$, what is $-9y - 3a - 3b - 9z - 9x - 3c$ ?
$= -3a - 3b - 3c - 9x - 9y - 9z$ $= (-3) \cdot (a + b + c) + (-9) \cdot (x + y + z)$ $= (-3) \cdot (9) + (-9) \cdot (-4)$ $= -27 + 36$ $= 9$